1. Field of the Invention
The present invention relates to an image recording apparatus, an image recording control method, and a storage medium. Particularly, the present invention relates to an image recording apparatus which is suitable in a case where an image is formed on a recording medium by a recording head having plural recording elements, an image recording control method which controls the image recording apparatus, and a storage medium which stores a program to execute the image recording control method.
2. Related Background Art
Conventionally, as an apparatus which forms an image on a recording medium such as a sheet, an OHP (overhead projector) sheet or the like, the apparatus in a form that a recording head of one of various recording systems is installed has been proposed. As the recording systems, there are a wire dot recording system, a thermal (thermosensitive) recording system, a thermal transfer recording system, an inkjet recording system and the like. In any of these recording systems, the recording head in which plural recording elements are united is generally used to increase recording efficiency.
In such a mechanism as above, striped density unevenness which originates in dispersion of recording elements and mechanical accuracy when the record head and the recording medium are shifted and moved could not be avoided. Concretely, in the inkjet recording system, a detailed stripe might be caused due to slight differences of ink discharge directions and ink discharge quantities among ink discharge nozzles acting as the recording elements, and also the striped density unevenness might be caused at recording medium shift interval due to an error of nozzle interval and an error of recording medium shift quantity.
As a method to correct such the density unevenness, for example, a multipass recording method as disclosed in Japanese Patent Application (Laid-Open) No. 60-107975 is used. Further, in order to prevent mischief due to interference between a thinning pattern and an image pattern in the multipass recording method, a recording apparatus which performs thinning by using a random mask pattern disclosed in, e.g. U.S. Pat. Nos. 5,818,474, 6,042,212 and 6,118,457 has been known.
The method using the random mask pattern will be briefly explained. In an image recording apparatus which causes a recording head having plural recording elements to scan an identical recording area on a recording medium plural times, creates a thinned-out image according to a thinning pattern in each scan, and completes an entire image, the random mask pattern of a predetermined size in which non-recording pixels and recording pixels are arranged at random is used as the thinning pattern for each recording area. In this method, since the image is formed by printed pixels according to the random mask pattern, the thinned-out arrangement does not have any pattern period. Thus, the density unevenness which is caused based on the number of recording pixels in the plural-time multipass recording at the same recording area according to the conventional multipass recording method is eliminated by suppressing periodicity of the density unevenness.
However, there are several drawbacks in the above conventional case. Namely, when the period of a random number is short, a repetitive pattern appears in the output image. Besides, when a uniform random number is used as the random number, graininess deteriorates due to the low-frequency component of the random number. Further, a printer ordinarily has plural printing modes in accordance with a priority of printing quality/printing speed and a kind of printing medium. However, in the above conventional case, there is a drawback that, since it is necessary to prepare the thinning pattern for each printing mode, many memories are necessary.
The present invention is made in consideration of the above drawbacks, and an object thereof is to provide, in a case where recording is performed by a multipass recording method, an image recording apparatus which can lower generation of repetitive pattern and deterioration of graininess as compared with a mask pattern based on a random number, an image recording control method for the image recording apparatus, and a storage medium which stores a program to achieve the image recording control method.
Another object of the present invention is to provide, in the case where the recording is performed by the multipass recording method, an image recording apparatus which can reduce the number of memories for storing the mask patterns, an image recording control method for the image recording apparatus, and a storage medium which stores a program to achieve the image recording control method.
In order to achieve the above objects, the present invention is characterized by providing an image recording apparatus which divides a recording head having plural recording elements into plural areas, performs plural-time scans to an identical area on a recording medium such as a sheet by using the same or different areas of the divided recording head, and creates a thinned-out image according to a thinning pattern in each scan to complete an entire image, the apparatus comprising:
mask creation means for creating plural mask patterns from a pseudo periodic mask arrangement that an arrangement of non-recording pixels and recording pixels becomes visually preferable; and
thinning means for thinning out recording data by using the mask patterns as the thinning patterns for respective recording areas by the recording head.
Further, in order to achieve the above objects, the present invention is characterized by providing an image recording control method which is applied to an image recording apparatus which divides a recording head having plural recording elements into plural areas, performs plural-time scans to an identical area on a recording medium such as a sheet by using the same or different areas of the divided recording head, and creates a thinned-out image according to a thinning pattern in each scan to complete an entire image, the method comprising:
a mask creation step of creating plural mask patterns from a pseudo periodic mask arrangement that an arrangement of non-recording pixels and recording pixels becomes visually preferable; and
a thinning step of thinning out recording data by using the mask patterns as the thinning patterns for respective recording areas by the recording head.
Further, in order to achieve the above objects, the present invention is characterized by providing a computer-readable storage medium which stores a program to execute an image recording control method applicable to an image recording apparatus which divides a recording head having plural recording elements into plural areas, performs plural-time scans to an identical area on a recording medium such as a sheet by using the same or different areas of the divided recording head, and creates a thinned-out image according to a thinning pattern in each scan to complete an entire image, the method comprising:
a mask creation step of creating plural mask patterns from a pseudo periodic mask arrangement that an arrangement of non-recording pixels and recording pixels becomes visually preferable; and
a thinning step of thinning out recording data by using the mask patterns as the thinning patterns for respective recording areas by the recording head.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.